Backup Sites: Cold, Warm, And Hot; Hardware And Software Availability - Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Chapter 8. Planning for Disaster

8.3.2. Backup Sites: Cold, Warm, and Hot

One of the most important aspects of disaster recovery is to have a location from which the recovery
can take place. This location is known as a backup site. In the event of a disaster, a backup site is where
your data center will be recreated, and where you will operate from, for the length of the disaster.
There are three different types of backup sites:
Cold backup sites
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Warm backup sites
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Hot backup sites
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Obviously these terms do not refer to the temperature of the backup site. Instead, they refer to the
effort required to begin operations at the backup site in the event of a disaster.
A cold backup site is little more than an appropriately configured space in a building. Everything
required to restore service to your users must be procured and delivered to the site before the process
of recovery can begin. As you can imagine, the delay going from a cold backup site to full operation
can be substantial.
Cold backup sites are the least expensive sites.
A warm backup site is already stocked with hardware representing a reasonable facsimile of that
found in your data center. To restore service, the last backups from your off-site storage facility must
be delivered, and bare metal restoration completed, before the real work of recovery can begin.
Hot backup sites have a virtual mirror image of your current data center, with all systems configured
and waiting only for the last backups of your user data from your off-site storage facility. As you can
imagine, a hot backup site can often be brought up to full production in no more than a few hours.
A hot backup site is the most expensive approach to disaster recovery.
Backup sites can come from three different sources:
Companies specializing in providing disaster recovery services
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Other locations owned and operated by your organization
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A mutual agreement with another organization to share data center facilities in the event of a disaster
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Each approach has its good and bad points. For example, contracting with a disaster recovery firm
often gives you access to professionals skilled in guiding organizations through the process of creating,
testing, and implementing a disaster recovery plan. As you might imagine, these services do not come
without cost.
Using space in another facility owned and operated by your organization can be essentially a zero-cost
option, but stocking the backup site and maintaining its readiness is still an expensive proposition.
Crafting an agreement to share data centers with another organization can be extremely inexpensive,
but long-term operations under such conditions are usually not possible, as the host's data center must
still maintain their normal production, making the situation strained at best.
In the end, the selection of a backup site is a compromise between cost and your organization's need
for the continuation of production.

8.3.3. Hardware and Software Availability

Your disaster recovery plan must include methods of procuring the necessary hardware and software
for operations at the backup site. A professionally-managed backup site may already have everything
you need (or you may need to arrange the procurement and delivery of specialized materials the site
does not have available); on the other hand, a cold backup site means that a reliable source for every
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